Previous studies have shown that mice exposed to TCDD (5ug/kg body weight) once weekly for 4 weeks, are more susceptible to infection, and that 5-day Thioglycollate induced peritoneal exudates contain significantly less lymphocytes and macrophages than controls. Present investigations are geared to determine whether this reduction in peritoneal cells is due to impaired chemotactic function or due to an antiproliferative effect on pro monocytes or macrophages. Either effect could contribute to increased susceptibility to infection with Salmonella bern.